Table 3.
Examples of Sample Sizes for Group-Randomized Designs
| Original Sample Size* | No. of Clinics | No. of Patients per Clinic (m) | ICC | VIF | Adjusted Sample Size* |
| 100 | 25 | 4 | .00 | 1.0 | 100 |
| 100 | 29 | 4 | .05 | 1.15 | 115 |
| 100 | 33 | 4 | .10 | 1.30 | 130 |
| 100 | 10 | 10 | .00 | 1.0 | 100 |
| 100 | 15 | 10 | .05 | 1.45 | 145 |
| 100 | 19 | 10 | .10 | 1.90 | 190 |
| 100 | 5 | 20 | .00 | 1.0 | 100 |
| 100 | 10 | 20 | .05 | 1.95 | 195 |
| 100 | 15 | 20 | .10 | 2.9 | 290 |
| 100 | 4 | 25 | .00 | 1.0 | 100 |
| 100 | 9 | 25 | .05 | 2.2 | 220 |
| 100 | 14 | 25 | .10 | 3.4 | 340 |
m = designator for number of patients per cluster to be used in calculations; ICC = intraclass correlation coefficient; VIF = variance inflation factor.
*Number of patients per treatment group.